Prosthetic joint components have long been known and used in the art. Examples include knee, hip and elbow replacements. Prosthetic components are available from manufacturers such as Zimmer, Inc. of Warsaw, Ind. To prepare the bone surfaces for attachment of the prosthetic components, it is often necessary to make a series of cuts in the bone or to remove portions of the bone to cause the bone to conform to the size and shape of the components which are to be attached thereto. Every surgeon strives for precise cuts, since the more precise the cut, the more likely is the prosthetic component to be anatomically correct. An anatomically correct component provides a superior result and will last longer than one that is not anatomically correct.
One situation in which such bone cutting is required is in the preparation of the femur and tibia for a total knee replacement. Exemplary knee replacements are available from Zimmer, Inc. under the trademark MGII. In particular, implantation of press-fit, non-cemented total knee components requires very precise bone cuts. In some prosthetics, an exact fit is required for the successful bone-ingrowth fixation of joint replacement components.
Typically, bone cuts are made by an oscillating saw or a reciprocating saw utilizing cutting guides or jigs stabilized by pinning and clamping. Various guides and methods for temporarily but rigidly securing these guides to the bone surfaces have been developed. Examples are found in U.S. Pat. Nos. 4,787,383; 4,825,857; and 5,129,909. In particular, in U.S. Pat. No. 5,129,909, screws are utilized for securing the guides to the bone so that the guide is held in compression against the bone. Proper and rigid affixation of the guides to the bone are required to assure reproducibly accurate bone cuts, prosthetic seating and lower limb alignment. However, some existing guides have been found to be undesirable because there was inadequate rigid fixation of the cutting block to the bone. As a result, in some cases, it was difficult, if not impossible, to predictably achieve a precise fit of the femoral component on the distal femur.
When cutting the bone, it is important that the guides be secured immovably to the bone and that the guides be secured with the same force at each point to prevent tilting of the guide. The load applied by a screw or other fixation device should be the same predetermined value at each point of attachment. The fixation device should also be able to accommodate lateral forces applied to the guides without allowing the guides to move and without releasing the load.
If screws are used, there is a risk of the surgeon stripping the threads if too much torque is applied to the screw after it seats, thus making it difficult, if not impossible, to secure the guide rigidly to the bone in the desired location. In addition, difficulty may be achieved in removing the screw from the bone once the cutting procedure has been completed.
It is therefor an object of the present invention to provide an improved system for affixing cutting guides and the like to bone surfaces for preparation of those surfaces for the attachment of a prosthetic component.
It is another object of the present invention to provide a fixation device for cutting guides and the like for preparation of a bone surface for attachment of a prosthetic component, which fixation device can be installed with a reproducibly accurate load and can be readily extracted thereafter.